Effects of drug resistance on viral load in patients failing antiretroviral therapy

• Published in: Journal of medical virology 2006-05, Vol.78 (5), p.608-613
• Main Authors: Machouf, N., Thomas, R., Nguyen, V.K., Trottier, B., Boulassel, M.R., Wainberg, M.A., Routy, J.P.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Anti-Retroviral Agents - pharmacology; Anti-Retroviral Agents - therapeutic use; antiretroviral drug failure; Biological and medical sciences; Canada; Cohort Studies; Cross-Sectional Studies; Disease Progression; drug resistance; Drug Resistance, Viral; Female; Fundamental and applied biological sciences. Psychology; Genes, Viral; genotypic testing; HIV; HIV Infections - diagnosis; HIV Infections - drug therapy; HIV Infections - virology; HIV Protease - genetics; HIV Reverse Transcriptase - genetics; HIV-1 - drug effects; HIV-1 - genetics; HIV-1 - isolation & purification; Human immunodeficiency virus 1; Human viral diseases; Humans; Infectious diseases; Male; Medical sciences; Microbiology; Middle Aged; Miscellaneous; Mutation; Species Specificity; Time Factors; Treatment Failure; V-shape relationship; Viral diseases; Viral Load; Virology
• ISSN: 0146-6615; 1096-9071
• DOI: 10.1002/jmv.20582

Previous studies on patients who develop drug resistant HIV‐1 variants have shown that continued use of failing regimens might provide clinical benefit. However, the effect of long‐term exposure to drug resistant variants may lead to emergence of compensatory mutations that may jeopardize this effect. In this study, we assess associations among type and number of drug resistant mutations, viral load and disease progression in patients with long‐term follow up. Patients with genotypic testing performed at the time of treatment failure were enrolled. Comparison of viral load and CD4 cell count between different resistance groups was performed using analysis of variance. Multiple linear regression analysis was performed to assess the simultaneous effects of the presence of particular mutations and their accumulation on viral load. Data from 475 patients who were followed for a median of 43 months from October 1999 to July 2005 were studied. A “V shape” relationship was observed between the number of mutations and viral load. Specifically, in patients harboring up to five mutations, viral load was reduced by 0.8 log/copies when compared to wild‐type variants. However, with more than six mutations viral load progressively increased. Certain reverse transcriptase mutations such as M184V/I, K70R, V108I, and protease mutations such as L33FIV, M84V, and M36I were associated with reduced viral load. Together, these findings suggest that long‐term maintenance of a sub‐optimal antiretroviral regimen may have deleterious consequences for the patient. J. Med. Virol. 78:608–613, 2006. © 2006 Wiley‐Liss, Inc.